Recently, in the manufacture of a semiconductor device, a chemical mechanical polishing (hereinafter briefly referred to as “CMP”) method has been widely used to flatten an insulating film, a metallic film, or a polycrystalline silicon film which is formed to fill a trench formed in a substrate. In the CMP method a chemical action resulting from a chemical is combined with a mechanical action resulting from abrasive grains to flatten a treatment target surface, specifically by supplying, onto an abrasive cloth, a polishing agent (slurry) including the abrasive grains and the chemical and bringing a treatment target into contact with the abrasive cloth.
However, the CMP method has a problem in that mechanical damage by the abrasive grains could not be avoided and a polishing damage might be caused to a treatment target surface.